# Ampere's Law in Classical Electrodynamics

1. Nov 20, 2011

### CHUKKY

I do not know but I do not know if Ampers law is valid for short conductors passing through a loop. I did integrate and my integral was different from the expected I*U. The law seems to be valid only when long conductors pass through a loop but not short ones. Can anyone explain what am missing?

2. Nov 20, 2011

### Matterwave

Ampere's law requires very strong symmetries to use properly. It's always valid, but the integral is very hard if edge effects are present.

3. Nov 20, 2011

### CHUKKY

but is their a way to show that no matter the dimension of the conductor passing through the loop the integral of the magnetic field along the loop is the enclosed current times the permeability constant.or was this law arrived by empirical and not theoretical means.

4. Nov 20, 2011

### Matterwave

Well, you need to modify Ampere's law a little bit to include the so-called "displacement current". It is "verified" theoretically because it is one of Maxwell's equations. But of course, all physical laws must be verified experimentally.

5. Nov 20, 2011

### CHUKKY

but wld displacement current avail for short conductor?nd it was a steady current.

6. Nov 21, 2011

### Matterwave

You need a current loop. The only reason you can neglect the "loop" part for the long wire is that you can say the other parts of the wire are far away. If you have a short conductor, you need to close the circuit to have current.

7. Nov 21, 2011

### CHUKKY

Awesome i just taught about that. kk And so what you saying is that due to the fact that electrons need to drift along the curved path, electric field intensity changes and Maxwell's law then avail right?if I am right reply me. And thank you very much for resolving this issue if my post is right. If my post aint right please correct.